Study On Catalytic Hydrogenation Of Diethyl Oxalate And Its Transesterification In Microchannels

Our country’s resource structure is lean oil and more coal.Utilizing coal resources reasonably,developing non-petroleum synthetic routes for chemical products and fine chemicals,and reducing the reliance on petroleum are of great significance for optimizing our country’s energy structure.Varieties of essential chemicals such as such as glycolate,ethyl methyl oxalate,ethylene glycol and ethanol can be prepared from syngas via the route of coal-based oxalate.Coal-to-diethyl oxalate has been preliminarily industrialized in our country.With the commissioning of many diethyl oxalate projects,it will inevitably lead to overcapacity.Therefore,the rational use of diethyl oxalate to synthesize other fine chemicals has drawn the attention of many researchers.In this paper,the catalytic transformation of diethyl oxalate has been carried out in several ways,and the following work was conducted:First,a series of silver-supported silica（Ag/Si O₂）catalysts were prepared by hydrogen peroxide reduction method,and the effect of different silver loadings on the catalytic hydrogenation of diethyl oxalate to ethyl glycolate was investigated.When the pressure is 1.5Mpa,the temperature is 245 ^oC and the silver loading is 10wt%,the Ag/Si O₂ catalyst has the best catalytic performance,the conversion of diethyl oxalate is 88.05%,the selectivity of ethyl glycolate is 82.76%,and its yield reached 72.87%.Compared to the catalytic performance of Ag/Si O₂ prepared by impregnation method,the catalyst prepared by hydrogen peroxide reduction method has higher catalytic activity.The result shows that the Ag/Si O₂ catalyst prepared by the hydrogen peroxide method has a higher adsorption and activation ability for H₂and diethyl oxalate,resulting in higher yield of ethyl glycolate.Secondly,a series of silver-supported Hollandite Mn O₂ catalysts（Ag/HMO）and silver-manganese composite catalysts（Ag-HMO）were prepared by hydrothermal combination with hydrogen peroxide reduction,and the effect of silver loading and calcination treatment on the catalytic performance of diethyl oxalate to acetal was investigated.The result shows that when the reaction pressure is 1.5 Mpa,the reaction temperature is 300 ^oC and the silver loading is20%,the Ag-HMO catalyst exhibits good activity,the conversion of diethyl oxalate is 88%and the selectivity of acetal is 58.3%.The study found that Hollandite Mn O₂ had a crystal lattice of0.47×0.47 nm,which could accommodate Ag atoms.During the calcination process of the Ag/HMO catalyst,Ag thermally migrates into the Hollandite Mn O₂ crystal lattice to form Ag-HMO catalyst.Due to the interaction between Ag and the carrier,a large number of Ag-O-Mn units are produced,which has a strong promotional effect on the adsorption and conversion of diethyl oxalate.Finally,a new type of microchannel reactor was used to carry out the research on the transesterification of diethyl oxalate and methanol to synthesize ethyl methyl oxalate,and the small reaction space and the separation effect of the fluid were used to achieve efficient mixing and mass transfer of reactants,thereby improving the process of catalytic activity.For this reactor,the effects of reaction time,molar ratio,catalyst concentration and reaction temperature on catalytic reaction activity were investigated,and a reaction temperature-response kinetic model was developed,which laid the foundation for the popularization and application of the process.